Size Matters

How much are you really eating? Probably more than you think. Here's how to judge for yourself.

Runners thrive on numbers–distance covered, time clocked, pace per mile And we're usually pretty good at calculating those accurately. But one area where most runners could use a little help with math is in figuring out how many calories we eat and how many we burn during our workouts. In fact, those five extra pounds that many runners drag around are proof-positive that many of us have trouble with simple addition and subtraction. We typically think we're eating fewer and burning more calories than we really are.

"In general, people will underestimate the calories in a typical meal by about 20 percent," says Brian Wansink, Ph.D., director of the Cornell Food and Brand Lab at Cornell University and author of *Mindless Eating* (Bantam Books, 2006). "But after a tough workout, you might underestimate how much you're eating by as much as 50 percent." His research group studied people training for a marathon and monitored them as they carbo-loaded in the lead-up to race day. The researchers found that on average the runners would guess that they had 1,500 calories on their plates when they actually had about 3,500 calories.

An extra 2,000 calories? That's almost a day's worth of food. Why are we so far off the mark? Turns out there are several factors, including our inability to accurately size up portions, external cues that cause us to overeat, and difficulties gauging our daily calorie budget. And any one of these factors–or some combination of them–can be enough to thwart our best efforts to drop extra pounds or maintain a goal weight. That said, losing a few pounds isn't rocket science. You simply need to take in fewer calories than you burn on most days of the week. With a few key strategies, you can accurately tally the number of calories you eat and burn daily. Learning how to size up your plate and your workouts will help you downsize your waistline.

The biggest weight-loss challenge is knowing exactly how much you're eating. It isn't easy. Restaurants typically dish out double and triple servings per entr? and food manufacturers sell megapackages of snack foods at discount prices, so it's difficult to determine a healthy portion of any food. And that's a big problem, since research has proven that we almost always eat nearly all of whatever is on our plates. A 2005 study published in the Journal of the American Medical Association found that people eat an average of 92 percent of any food they serve themselves.

"Part of the problem is labeling, because packages don't tell us in a systematic way how many calories there are per portion," says Barbara Rolls, Ph.D., professor of nutritional sciences at Penn State University and author of The Volumetrics Eating Plan (Harper Collins, 2005). "What is labeled as a serving size varies randomly even in the same category of food." For example, a serving of Chips Ahoy chocolate-chip cookies is three cookies, while for Fig Newtons, it's just two. Serving sizes also don't take into account the calorie density of a food. Other countries provide information on nutritional labels that tells how many calories are in 100 grams of the product, which makes it very easy to compare one food with another. "If you see how many calories are in 100 grams of two different types of potato chips, you immediately know which chip is more caloric," says Rolls.

Numerous studies have confirmed this calorie confusion. Wansink and his colleagues have tested various theories about portions and serving sizes, and the results all point to the fact that we tend to equate the size of the bag or box a food comes in with how much of it we should eat. "Six 100-calorie servings in separate bags is six servings," says Wansink. "Empty them all out into one big 600-calorie bowl, and one serving is now however much we want to eat." The bigger the meal we're eating, the harder time we have estimating its calories (remember those carbo-loading marathoners piling 3,500 calories on their plates). "We get more optimistic about the number of calories we think we're eating as the meals get larger," says Wansink.

As if knowing a reasonable serving size weren't hard enough, external factors also trigger overeating. Where you are, what you're doing, and who you're with all affect how many calories you're likely to consume. When you're in a restaurant with low lighting, you tend to eat more. You also eat incrementally more as the number of people at the dining table increases, and you'll eat more if you're watching television or reading the newspaper. According to Wansink, eating in front of the TV can increase your consumption as much as 60 percent, depending on how long you sit there watching.

The size of the plates we eat from, the bowls we serve from, and the utensils we use can also make us eat more than we mean to. Wansink has found that when we serve ourselves from bigger bowls and use larger serving spoons, we scoop up at least 25 percent more. Yet when we make the simple switch to eating off of smaller plates–making the amount we put on them look larger–we automatically eat at least 25 percent less.

But you don't have to eat on a mini plate all by yourself in a brightly lit spot with no television or reading material to eat sensibly. Just being aware of these factors can help you consume less. Something as simple as using large bowls for low-cal foods like salad and small bowls for ice cream can make the difference between losing and gaining a few pounds.

Once you've mastered portion sizes and shutting out external eating cues, your work isn't done. Most of us still don't have a clue about how many calories we should be eating every day, a number that is influenced by age, gender, height, weight, and activity level (for a simple calculator, try dietdetective.com). Once you determine that you should be eating, say, about 2,200 calories a day, you can divide that throughout the day to figure out about how much you should be eating at each meal. "Get a rough idea of your calorie needs that you can use as a starting point, and then adjust up or down depending on your weight goals," says Rolls. With your calorie budget in hand, you can keep a food-and-exercise diary to document how much you really eat and burn on a daily basis (see "Eat, Exercise, Take Notes,") so that you can compare it to your actual calorie needs.

As most people find when they start keeping a food diary, it's not the occasional slice of death-by-chocolate cake that does us in. It's what Wansink calls the "mindless margin"–approximately 100 calories extra each day that we take in through larger portions or incidental snacking that make the difference between gaining or losing a few pounds over a year. Of course, if we continue eating these mindless calories over several years, they can add up to significant weight gain. But the good news is that losing those two or three last pounds in a year requires cutting only about 25 calories from your diet each day or burning 25 extra during your daily workouts.

While running is one of the most effective activities for burning calories, it's still a lot easier to eat–or not eat–25 calories (a Hershey's Kiss) than it is to run them off (at least a quarter mile). And that's why runners who spend months training for a marathon might still be carrying a few extra pounds as they cross the finish line. "There's also a big variable in the energy cost of running–which differs between genders, ethnicities, age, weight–which can result in 10 to 15 percent variances in how much weight two different runners might lose," says Ralph La Forge, M.Sc., a physiologist at Duke University. If you've always relied on the notion that 35 miles of running will burn exactly 3,500 calories and, therefore, result in the loss of one pound of body weight, you're missing out on an important part of the equation.

As La Forge explains, that 100-calories-per-mile standard (which is built into the readouts on your gym's treadmills) is the gross energy cost of running–strictly how many calories you burn going from point A to point B. But runners who are trying to lose weight need to also know the net energy cost of their runs so that they can more accurately calculate their entire calorie burn for the day. For example, if you go for a three-mile run and it takes a half hour, you need to subtract out however many calories you would have burned during those 30 minutes even if you'd been just sitting at your desk (about 80 calories). That means the true net energy cost of your run over the course of the day is more like 220 calories than 300.

It's also important for weight-conscious runners to factor in what La Forge calls "energy conservation." "About a third of us wipe out almost half of the energy expenditure of a workout by conserving energy afterward," he says. If your long run leaves you so exhausted that you spend the rest of your Saturday on the couch watching movies rather than cleaning the house or working in the garden, you may end up burning fewer calories throughout the day than if you did a slightly shorter run but still had the energy to take the kids to the park in the afternoon for batting practice. And, of course, you have to beware of "energy compensation"–better known as eating more calories after a workout than you burned off during the run. "I met a guy who ran purely because he liked ice cream," says Wansink. "But to equal his daily pint, he needed to run 12 miles every day." Most of us don't (or can't) do that.

"If you're exercising primarily for health, none of this matters that much," says La Forge, who takes note of the many benefits of exercise, including its link to a reduced risk of chronic diseases such as diabetes and heart disease. But if you're running to lose weight, you have to keep in mind all the variables. "I believe in exercise," says Wansink. "But I also know how quickly you can eat many more calories than you will run off in a normal workout."